The present invention relates to a method of manufacturing an electronic device including a semiconductor device.
In accordance with recent high integration of electronic devices including semiconductor devices, patterns used for the manufacture of the devices have become more and more refined. For example, in a process for patterning a gate electrode of a MOS transistor used in a dynamic random access memory (DRAM), a microcomputer or the like from a polysilicon film, a gate processing technique using a hard mask such as a silicon nitride film has been put in practical use. In photolithography preceding this gate processing, in order to further refine a resist mask, a resist film to be used has become thinner and thinner so as to improve the resolution of the resist mask and increase the depth of focus.
In this case, in dry etching for forming a gate electrode by patterning a polysilicon film, a WSi polycide film and a polymetallic film, a resist film serving as an etching mask is partially etched. Therefore, the thickness of the resist film is decreased (or the resist film is removed in some cases), resulting in degrading the patterning accuracy. As a technique to overcome this problem, a hard mask of a nitride or oxide film having high selectivity against polysilicon, WSi polycide and polymetal is formed on the polysilicon film, the WSi polycide film and the polymetallic film. Specifically, not only the resist film but also the hard mask are used as a mask in the patterning, so that the problem derived from the thickness decrease of the resist film can be solved.
As another example of the formation of a surface protecting film as described above, a process for forming a SAC (self align contact) will be described. In the SAC process, there is no need to align a mask for a gate electrode against a mask for a contact but it is necessary to definitely prevent contact between the gate electrode and the contact. Therefore, a surface protecting film (hard mask) of a silicon nitride film is formed on the gate electrode, so that the upper surface of the gate electrode can be definitely prevented from coming in contact with the contact. When the surface protecting film is to be formed on the gate electrode in this manner, conductive films for the gate electrode (such as a polysilicon film, a polycide film and a polymetallic film) and a silicon nitride film are deposited, and thereafter, a resist mask formed thereon is used in successively etching the silicon nitride film, the polysilicon film and the like.
The etching carried out in this case will now be described. FIGS. 22(a) through 22(c) are sectional views for showing conventional procedures for successively etching the nitride film and the polysilicon film.
In the procedure shown in FIG. 22(a), a gate oxide film 102 with a thickness of 10 nm and a polysilicon film 103 with a thickness of 250 nm are successively formed on a silicon substrate 101, and a silicon nitride film 104 with a thickness of 150 nm is deposited on the polysilicon film 103. Thereafter, the silicon nitride film 104 is coated with a chemically amplified resist, which is formed into a resist mask 105 by photolithography using KrF excimer laser.
Next, in the procedure shown in FIG. 22(b), the resist mask 105 is used as an etching mask for etching the silicon nitride film 104, thereby forming a surface protecting film 106.
Then, in the procedure shown in FIG. 22(c), without removing the resist mask 105, the underlying polysilicon film 103 is etched, so as to form a polysilicon pattern 108 functioning as a gate electrode above an active area. At this point, as is shown in FIG. 22(c), the resist mask 105 is etched to some extent and the lateral dimension and shape thereof are spoiled, but the surface protecting film 106 of the silicon nitride film having high etching selectivity against polysilicon is scarcely etched. In other words, the polysilicon pattern 108 is formed by using the resist mask 105 and the surface protecting film 106 as the mask.
Also, in a process for forming a metallic line by patterning a metallic film, the metallic film for the line is conventionally patterned by using a hard mask for metal in some cases.
FIGS. 23(a) through 23(d) are sectional views for showing the conventional procedures for forming a metallic line layer.
First, in the procedure shown in FIG. 23(a), a TiN film 112 with a thickness of 50 nm, an aluminum film 113 with a thickness of 0.45 xcexcm and a TiN film 114 with a thickness of 30 nm are successively deposited by reactive sputtering and general sputtering on a silicon oxide film 111 (such as an interlayer insulating film or an isolation insulating film) formed on a substrate. On the TiN film 114, a silicon oxide film 115 with a thickness of 150 nm is deposited by plasma CVD.
Thereafter, the silicon oxide film 115 is coated with a chemically amplified resist so as to form a resist film, which is formed into a resist mask 116 with a thickness of 0.7 xcexcm by the lithography using KrF excimer laser.
Then, in the procedure shown in FIG. 23(b), the silicon oxide film 115 is dry etched by using a dry etcher with the resist mask 116 used as an etching mask. Thus, a hard mask 117 for metal is formed. At this point, the TiN film 114 is also partially etched through over-etching.
Next, in the procedure shown in FIG. 23(c), the resist film 116 is removed through ashing and cleaning. The ashing is conducted by a down stream method using microwaves, and an aqueous solution of ammonium fluoride is used as the cleaning solution.
Thereafter, in the procedure shown in FIG. 23(d), by using the hard mask 117 for metal as an etching mask, the underlying metallic films (the stacked films including the TiN film 114, the aluminum film 113 and the TiN film 112) are etched by using a metal dry etcher, thereby forming a metallic pattern (metallic line) 119.
However, since the silicon nitride film and the underlaying polysilicon film and the like are successively etched as described above referring to FIGS. 22(a) through 22(c), the dimension of the polysilicon pattern 108 formed by dry etching the polysilicon film and the like can be much larger than the dimension of the surface protecting film 106, and the shape of the polysilicon pattern 108 can be spoiled (which are designated as pattern defects).
The present inventors studied the cause of these defects, resulting in finding the following: After etching the silicon nitride film 104 in the procedure shown in FIG. 22(b), a small deposition 107 with a size of 0.03 xcexcm or less is grown as a contaminant in the vicinity of the interface between the resist mask 105 and the surface protecting film 106. This deposition 107 works as an etching mask for the polysilicon film 103, resulting in causing a pattern defect that the dimension of the polysilicon pattern 108 partly deviates from the designed dimension. It was found that such phenomenon occurs not only when a polysilicon film is formed below a silicon nitride film but also a W (tungsten) film, a silicon oxide film, a WSi (tungsten silicide) film, a silicon oxinitride film or the like is formed below.
When the polysilicon film 103 formed below the silicon nitride film 104 is not continuously etched after etching the silicon nitride film 104, the deposition 107 formed on the side of the surface protecting film 106 can be easily removed by ashing, or cleaning the wafer with sulfuric acid-hydrogen peroxide (an aqueous solution of sulfuric acid and hydrogen peroxide) or ammonia-hydrogen peroxide (an aqueous solution of ammonia and hydrogen peroxide). However, the resist mask 105 serving as the etching mask is also removed through this process. When the polysilicon film 103 is etched by using the surface protecting film 106 alone as the mask with the resist mask 105 removed, the surface protecting film 106 cannot be prevented from being etched at all but can be etched to some extent, resulting in decreasing the thickness of the surface protecting film 106 to some extent. Since it is difficult to control the etch amount of the surface protecting film 106 in this case, the thickness of the surface protecting film 106 is varied between lots. Therefore, it is difficult to accurately attain the predetermined designed thickness of the surface protecting film 106. Since it is necessary to accurately control the thickness of the surface protecting film 106 in the SAC process, it is desired to avoid removal of the resist mask 105 as far as possible.
Furthermore, it was found, also in the process for forming the metallic line, that a deposition 118 is locally grown as a contaminant on the TiN film 114 after the etching for forming the hard mask 117 for metal as is shown in FIG. 23(b). Such a reaction product exists comparatively unstably, but when the underlying metallic films (including the TiN film 114, the aluminum film 113 and the TiN film 112) are etched with the deposition 118 remaining, the deposition 118 works as a micromask as is shown in FIG. 23(d), resulting in forming an etching remainder portion 120 (pattern defect) in the metallic pattern 119 formed by patterning the metallic films. In addition, when the substrate is exposed to the air with the deposition 118 remaining, it is difficult to remove the deposition 118 even through ashing and cleaning are carried out thereafter.
An object of the invention is suppressing pattern defects from being caused after patterning an underlying layer by providing means for effectively removing the aforementioned deposition or suppressing the growth of the deposition after successively etching a hard mask film and the underlying layer below.
The first method of manufacturing an electronic device of this invention comprises the steps of (a) forming, on an underlying layer, an insulating film made from one of an oxide film, a nitride film, an oxinitride film and an organic-inorganic hybrid film; (b) forming a resist pattern on the insulating film; (c) forming an insulating film pattern by etching the insulating film with the resist pattern used as a mask; (d) conducting a plasma treatment on exposed portions of the underlying layer and the insulating film pattern without removing the resist pattern after the step (c); and (e) etching the underlying layer with the resist pattern and the insulating film pattern used as a mask.
In this method, a deposition grown in the vicinity of the interface between the resist pattern and the insulating film pattern is removed through the plasma treatment carried out after etching the insulating film. Accordingly, the resultant electronic device includes few pattern defects in an underlying layer pattern formed from the underlying layer.
In the first method of manufacturing an electronic device, the plasma treatment can be conducted by using a gas including at least one of a N2 gas, an O2 gas and an inert gas in the step (d).
In the first method of manufacturing an electronic device, when the underlying layer is made from one of a monosilicon layer, a silicon substrate, a polysilicon film, an amorphous silicon film, an organic film, an organic-inorganic hybrid film, a nitride film and an oxide film, the underlying layer can be etched with a chlorine-containing gas or a bromine-containing gas in the step (e). Such etching gases exhibit the etching function by utilizing a radical reaction, and hence are advantageous in minimally damaging a silicon layer.
In this case, when the insulating film is a silicon nitride film, the insulating film of the silicon nitride film can be etched with a fluorine-containing gas in the step (c).
The underlying layer is preferably one of a surface portion of a silicon substrate, an electrode, an interconnect and an interlayer insulating film.
The second method of manufacturing an electronic device of this invention comprises the steps of (a) forming an insulating film on an underlying layer; (b) forming a resist pattern on the insulating film; (c) forming an insulating film pattern by etching the insulating film with the resist pattern used as a mask; (d) cleaning the underlying layer after the step (c); and (e) etching the underlying layer with at least the insulating film pattern used as a mask.
In this method, a deposition grown in the vicinity of the interface between the resist pattern and the insulating film pattern is removed by cleaning the underlying layer after etching the insulating film. Accordingly, the resultant electronic device includes few pattern defects in an underlying layer pattern formed from the underlying layer.
In the second method of manufacturing an electronic device, when water is used as a cleaning solution in the step (d), the deposition can be definitely removed without leaving any impurity on the substrate.
In this case, when the cleaning solution is kept at 50xc2x0 C. or more, the deposition can be more effectively removed.
In the second method of manufacturing an electronic device, when the deposition is made from an acidic material, an aqueous solution of TMAH (tetramethyl ammonium hydride) is preferably used as a cleaning solution in the step (d), and when the deposition is made from an alkaline material, a diluted hydrofluoric acid aqueous solution is preferably used as a cleaning solution in the step (d).
In the second method of manufacturing an electronic device, when the insulating film is a silicon nitride film or a silicon oxinitride film, the method can further comprise a step of exposing a substrate to the air between the step (c) and the step (d). Also in this case, the effect to remove the deposition can be exhibited as far as the insulating film is a silicon nitride film or a silicon oxinitride film.
In the second method of manufacturing an electronic device, when the underlying layer is made from one of a monosilicon layer, a silicon substrate, a polysilicon film, an amorphous silicon film, an organic film, an organic-inorganic hybrid film, a nitride film and an oxide film, the underlying layer can be etched with a chlorine-containing gas or a bromine-containing gas in the step (e). Such etching gases exhibit the etching function by utilizing a radical reaction, and hence are advantageous in minimally damaging a silicon layer although not used in etching polysilicon and a metal.
In this case, when the insulating film is a silicon nitride film, the insulating film of the silicon nitride film can be etched with a fluorine-containing gas in the step (c).
The third method of manufacturing an electronic device of this invention comprises the steps of (a) forming an insulating film on an underlying layer; (b) forming a resist pattern on the insulating film; (c) forming an insulating film pattern by etching the insulating film with the resist pattern used as a mask; (d) conducting a heat treatment on a substrate without removing the resist pattern after the step (c); and (e) etching the underlying layer with the resist pattern and the insulating film pattern used as a mask.
In this method, the heat treatment is conducted after etching the insulating film, thereby removing a deposition grown in the vicinity of the interface between the resist pattern and the insulating film pattern. Accordingly, the resultant electronic device includes few pattern defects caused in an underlying layer pattern formed from the underlying layer.
In the third method of manufacturing an electronic device, when the heat treatment is conducted under vacuum in the step (d), the growth of the deposition can be suppressed because a water component is not absorbed by the resist pattern and the insulating film pattern.
The fourth method of manufacturing an electronic device of this invention comprises the steps of (a) forming an insulating film on an underlying layer of titanium nitride; (b) forming a resist pattern on the insulating film; (c) forming an insulating film pattern by etching the insulating film with the resist pattern used as a mask; (d) conducting a plasma treatment on exposed portions of the underlying layer and the insulating film pattern after the step (c); and (e) etching the underlying layer with the insulating film pattern used as a mask by using a halogen-containing gas.
The fifth method of manufacturing an electronic device of this invention comprises the steps of (a) forming an insulating film including nitrogen on an underlying layer; (b) conducting a heat treatment on the insulating film for removing NHx, wherein x is an arbitral value; (c) forming a resist pattern on the insulating film; (d) forming an insulating film pattern by etching the insulating film with the resist pattern used as a mask; and (e) etching the underlying layer with the resist pattern and the insulating film pattern used as a mask.
In this method, the insulating film is etched after removing an impurity through the heat treatment, and hence, a reaction product can be prevented from being produced in etching the insulating film. Accordingly, the growth of a deposition in the vicinity of the interface between the resist pattern and the insulating film pattern can be suppressed, and hence, the resultant electronic device includes few pattern defects caused in an underlying layer pattern formed from the underlying layer.
The sixth method of manufacturing an electronic device of this invention comprises the steps of (a) forming an insulating film on an underlying layer; (b) forming a protecting film on the insulating film; (c) forming a resist pattern on the protecting film; (d) forming an insulating film pattern by etching the protecting film and the insulating film with the resist pattern used as a mask; and (e) etching the underlying layer with the resist pattern and the insulating film pattern used as a mask.
In this method, since an impurity can be prevented from spreading upward from the insulating film by the protecting film, a reaction product can be prevented from being produced in etching the insulating film and the protecting film. Accordingly, the growth of a deposition in the vicinity of the interface between the resist pattern and the insulating film pattern can be suppressed, and hence, the resultant electronic device includes few pattern defects caused in an underlying layer pattern formed from the underlying layer.
In the sixth method of manufacturing an electronic device, when the insulating film is a silicon nitride film, the protecting film can be an oxide film formed by oxidizing a surface portion of the insulating film in the step (b).